Off-peak water heating system



Dev. 16, 19 c. M. OSTERHELD 2,266,243

OFF-PEAK WATER HEATING SYSTEM Filed July 15, 1940- INVENTOR CL ARk 0s TERHELD b BY z Z ATTORN EY Patented Dec. 16, 1941 OFF-PEAK WATER HEATING SYSTEM Clark M. Osterheld, Stoughton, Wis., assignor to McGraw Electric Company, Eigin, 11]., a corporation of Delaware Application July 13, 1940, Serial No. 345,297

9 Claims.

My invention relates to water heating systemsand particularly to off-peak water heating sys- An object of my invention is to provide a relatively simple control system for delaying the start of the heating of water in a water-containing tank for predetermined fixed lengths of time after the start of the offeak period, the delay increasing in proportion to the amount of hot water in the tank.

Another object of my invention is to provide a relatively simple and efllcient control system for a water tank that shall be rendered operative during only the oil-peak period.

Still another object of my invention is to provide an oil-peak water heating system that shall cause the heating period to occur during substantially the middle part of the off-peak period and to be terminated by the action of thermal control means.

Other objects of my invention will either be apparent from a description of one form of system embodying my invention or will be pointed out in the course of a description thereof and particularly in the appended claims.

In the drawing,

Figure 1 is a view in vertical section of a hot water tank and a diagram of connections of the timer and of the various thermally-actuable switches controlled thereby, and Fig. 2 is a fragmentary view of a modified form of timer contact means.

A domestic hot water tank Ii is of the usual cylindrical type having a height several times greater than its diameter and is provided with a cold water inlet pipe l3 and a hot water outlet pipe I5. While I have illustrated the tank ll sectionally only, I desire it to be understood that it may be covered with suitable heat-insulating material, may also be provided with an outer protective casing and may be supported in any suitable or desired manner, all of these details constituting no partof my invention and further detailed illustration and further description thereof being therefore thought unnecessary.

A clamp-on electric heater I1 is shown schematically only and while I prefer to use the flexible clamp-on heater disclosed and claimed in my co-pending application Ser. No. 315,890, I do not desire to be limited thereto although it may be pointed out that I prefer to use a clampon heater rather than to provide and use a heating unit inserted into the tank through a suitable opening in its wall.

numeral I! may comprise a small synchronous motor 2|, the terminals of which are connected by suitable conductors to supply circuit leads 23 and 25. The motor 2| operates a worm 21 which is in operative and driving engagement with a circular disc 29 mounted on ashaft 3 l The shaft 3| has mounted thereon a cam disc 33 which has one part 35 thereof of a given outer radius, while another part of the peripheral surface of the disc 33 has a larger outer radius and is designated by 31. This portion 31 of the periphery is shown to extend for substantially one-third of the periphery of the disc and since the shaft 3| and the member 29 are desired to be rotated through one full revolution in twenty-four hours, the time extent of portion 31 will be substantially eight hours. It may be here pointed out that this length of time is that of the usual oil-peak period and may be considered, for instance, to extend from 10 p. m. to 6 a. m. I desire to point out further that the disc 33 may be constructed to provide an oil-peak period which is less than eight hours or which is greater than eight hours and that it may be so mounted on the shaft 3| that the beginning of this oil-peak period will occur at some other time than 10 p. m.

The shaft 3| has also mounted thereon a contact arm 38 which is adapted to move over a dial 4| which dial may be supported in any manner now well known in the art. While I have not shown any supporting means for the shaft 3| and for the driving motor 2i, these are, of course, to be provided and may take any form and construction now well known in the art.

While I have illustrated an electric motor as part of the timing means, I do not wish to be limited thereto as any other timing means, such as a clock, may be used by me.

A timer or clock-actuated heater control switch comprises a substantially rigid contact arm 43 and a resilient contact arm 45, the latter being normally biased away from its cooperating contact arm 43 and being forced into engagement therewith when the portion 31 of the disc 33 has been turned into substantially the position shown in the drawing where this portion engages a ing 41 on contact arm 45 to cause the latter to move into engagement with contact arm 43. The supply circuit conductor 23 is electrically connected to contact arm 43, while contact arm 45 is connected through a conductor 49 to a main contact member SI of a contactor designated generally by the numeral 53. The other main contact member is connected by a conductor 51 to one A timing means designated generally by the 55 terminal of the electric tank heater I1, while the other terminal thereof is connected through a conductor 59 to the other supply circuit lead 25.

The contactor 53 includes also a coil 8| which is adapted to energize an armature core 63 having connected therewith a main contact bridging member 85 as well as an auxiliary contact bridging member 61 which latter is adapted to close a holding circuit for the contactor as will be hereinafter described in detail. One terminal of the coil 6| is connected by a conductor 89 to the conductor 49 while the other terminal of coil BI is connected by a conductor II with an auxiliary contact member 13. The other auxiliary contact member 15 is connected by a conductor ll with a substantially stationary or rigid contact arm I9 of a thermally-actuable switch 8|. This thermally-actuable switch 8| includes an expansion rod 83 which may be encased in a tubular member 85 mounted in the wall of the tank II and extending into the tank to be immersed in the water therein and, as shown in Fig. 1 of the drawing, this thermally-actuable switch 8| is positioned in the lowermost part of the tank. The switch 8| includes also a substantially resilient contact arm 81 which is adapted to be engaged with and disengaged from the contact arm 19 by means of the expansion and contraction of the rod 83. It is to be understood that the contact arm 81 is normally biased into engagement with the contact arm 19 when permitted to do so by reason of the subjection of the expansion rod 83 to cold water causing the expansion rod to contract and permit engagement of the contact arms 19 and 81.

The dial 4| has mounted thereon a plurality of fixed contact members 89, 9| and 93 and while I have shown these contact members as being positioned on the dial to be engaged by the contact arm 39 at 10 p. m., 12 p. m. (midnight) and 2 a. m.,-I do not desire to be limited thereto I and it is to be understood that these contact members may be positioned at any desired points peripherally of the dial and with any desired space between adjacent contact members.

I provide further a plurality of auxiliary thermally-actuable switches and I have shown two such switches, 95 and 91, each of which includes a tubular member 99, an expansion rod I| therein, a substantially resilient contact arm I03 and a substantially rigid contact arm |05, arm I03 being normally biased into engagement with arm I when permitted to do so by reason of the contraction of expansion rod |0| when the tube 99 is immersed in cold water or in water having a temperature below a predetermined value. Contact member 89 is connected by a conductor I01 with contact arm I05 of the uppermost thermally-actuable switch 95. Contact member 9| is connected by a conductor I09 with contact arm I05 of the next lower thermallyactuable switch 91. Contact member 13 of the contactor 53 is connected through a conductor H3 with contact arm 39.

I wish to point out that I have shown the thermally-actuable switches 8|, 95 and 91 schematically only and as comprising expansion members but I desire it to be understood that this is done for illustrative purposes only and that I may employ any known kind of thermally-actuable members for the intended purpose. Further, I have illustrated the dial 4| and the rotating contact arm 39 generally only and the same comments as to the actual construction thereof as made with regard to the thermally-actuable switches apply here also. It may be here pointed out further that the contact arm 39 indicates the time of day.

The operation of my system is substantially as follows: the timer motor 2| is operative at all times when the supply circuit, including particularly the leads 23 and 25 is energized, and

the contact arm 39 will therefore be efiective to indicate the time of day. If it be assumed that the central station operator prefers to have the off-peak period extend from 10 p. m. to 6 a. m., the peripheral extent of the portion 31 of disc 33 will be for one-third of the entire periphery and the disc 33 will be so mounted on the shaft 3| that contact arm 45 will be moved into engagement with contact arm 43 at substantially 10 p. m. At substantially the same time'contact arm 39 will engage fixed contact member 89 and an energizing circuit will be closed through coil SI of contactor 53 if only the very uppermost portion or part of tank II is filled with hot tank extending upwardly therein to such a height as to submerge the tube 99 of thermally-actuable switch 95. The energizing circuit through coll 6| will extend from supply circuit lead 23 through contact arms 43 and 45, conductor 49, conductor 69, coil 6|, conductor II, conductor 3, contact arm 39 to contact 89, conductor I01 to contact arm I05 of thermal switch 95, to contact arm I03 and through a conductor M5 to conductor 59 and from there to the other supply circuit lead 25. As stated above, this circuit is established if the thermally-actuable switch 95 is immersed in cold water or in water the temperature of which is below a predetermined value.

The energized coil 6| will cause upward movement of armature core 63 and simultaneous upward movement of contact bridging members and 61. Contact bridging member 65 will engage contacts 5| and 55 to thereby cause closing of the electric circuit including the electric heater II which will therefore be energized and will start to heat up the cold water in the lower portion of the tank.

As it is obvious that contact arm 39 will move out of engagement with fixed contact member 89 in a relatively short time, it is necessary to have a holding circuit for the coil 6| of contactor 53 and this circuit is established as follows: from supply circuit lead 23 through contact arms 43 and 45, conductors 49 and 69, coil 6|, conductor II, contact I3, contact bridging member 61, contact 15, conductor 11 to contact arm I9 of the lowermost thermally-actuable switch 8|, through contact arm 81 and from there through conductors H5 and 59 to the other supply circuit lead 25. This will cause continuous closure of the contact members of the contactor 53 to thereby continue energization of the heater The capacity in watts of the electric heater I! has been so selected that the cold water in the tank will be heated to apre-decided higher temperature within the eight hour period during which the circuit, including particularly the contactor and the electric heater, is conditioned or prepared for the hereinbefore described operative condition. That is, I prefer to cause deenergization of the tank heater I! by the lowermost thermally-actuable switch 8| and I desire to here point out that the contacts of this switch are connected in the holding circuit of the contactor, as hereinbefore described.

Let it be assumed that the uppermost auxiliary thermally-actuable switch 95 is immersed in hot water so that contact arm I03 will be out of engagement with contact arm I05, in which case the hereinbefore described circuit through the electric heater I! prepared by closure of the first mentioned switch including contact arms 43 and 45, effected by the timing means will not have occurred and energization of the electric heater I! will be delayed for a predetermined fixed time. If the tank contains enough hot water in the upper part to surround thermal switch 95, but not to surround thermal switch 91, contact member 9|, mounted on dial 4| to be engaged by contact arm 39 at 12 p. :11. (midnight), will cause the hereinbefore described operation of the contactor to occur. Energization of the electric heater I! will therefore begin at substantially 12 p. m. and it may be here pointed out that the amount of cold water in the tank is less than that which would cause energization of the electric heater to be eiiected at 10 p. m.

The position of the plurality of auxiliary thermally-actuable switches 95 and 91 has been or will be so selected and the adjustments of not only these thermally-actuable switches but also of the lowermost thermally-actuable switch 8| will be made such that, in cooperation with the heating capacity of the heater ll, heating of the cold water in the tank will be effected before the expiration of the off-peak period and opening of the mechanically-actuable switch comprising contact arms 43 and 45.

Contact member 93 has hereinbefore been described as being mounted on the dial 4| at a point thereon to be engaged by contact arm 39 at substantially 2 a. m. and if the quantity of hot water in the upper portion of the tank was such as to submerge both thermally-actuable switches 95 and 91 in hot water whereby contact arms H13 in each were out of engagement with their cooperating contact arms I05, engagement of arm 39 with contact 93 would cause energization of heater I! through the following circuit and in the following manner. A circuit would be established from supply circuit lead 23 through contact arms 43 and 45, conductors 49 and 69, coil 5|, conductors H and H3, contact arm 39 to contact member 93 and from there through conductors H I and 59 to the other supply circuit lead 25. Energization of coil 6| would result in the same actions as have hereinbefore been described as occurring because of operation of either the uppermost thermally-actuable switch 95 or the next lower thermally-actuable switch 91 whereby to cause an energizing circuit through the heater IT, or, as hereinbefore set forth in detail.

It may be pointed out here that the system shown in Fig. 1 is not arranged to recognize changes in the amount of hot water in the tank when these changes occur after 10 p. m. and before 12 midnight or after 12 midnight and 2 a. m. Let it be assumed, for example, that the amount of hot water in the upper part of the tank was such that thermally-actuable switch 95 was submerged in hot water at 10 p. m. when contact arm 39 engaged contact 89, but that such a quantity of hot water was drawn from the tank, say at 10:15 p. m., that switch 95 was then submerged in cold water. While immediate energization of the heater I1 would be desirable this can not be effected until 12 p. m. midnight.

Referring now to Fig. 2 of the drawing I have there shown a modified control dial which will permit energization of the tank heater at any instant between predetermined time limits it hot water is withdrawn from the tank as above described. I provide fixed contacts H1 and H9, each of arcuate shape, adapted to be initially engaged by contact arm 39 at 10 p. m. and 12 p. m. midnight respectively. The peripheral lengths of the contacts is such that contact H1 extends substantially up to contact H9 and contact H9 extends substantially up to a third contact HI (2 a. in. contact) this latter contact taking the place of contact 93. The connections of contacts H7, H9 and I2! are the same as hereinbefore described for contacts 89, 9| and 93.

It is evident that if, at 10 p. m., thermallyactuable switch is surrounded by hot water, the tank heater I1 will not be energized at that time, but if, by reason of the withdrawal of hot water from the tank at 10:15 p. m. or at any time before 12 p. m. midnight, switch 95 is surrounded by cold water, the system including the dial of Fig. 2 will cause energization of the tank heater as soon as switch 95 is submerged in cold water. The delay in energization of the tank heater is not a predetermined length of time determined by the positions of the fixed contact members, but by the amount of hot water remaining in the tank during the early part of the off-peak period.

While I have shown an electric motor as operating the timing means, I do not desire to be limited thereto since any other form of continuously operative timing means such as a mechanical clock may be utilized by me. However, it is, of course, evident that a timing means driven by a small synchronous electric motor constitutes a relatively simple and continuously operative timing means. Further, as has already been hereinbefore stated, while I have shown the use of expansion rods as the thermal elements, I do not desire to be limited thereto so long as thermally-actuable elements operative in a similar manner to obtain the hereinbefore described results is to be assumed as included in my invention.

The system embodying my invention thus comprises in one modification, a relatively simple means for delaying energization of an electric heater associated with a hot water tank for predetermined but different times of delay, in accordance with the. amount of cold water in a tank, it being understood, however, as has already been hereinbefore noted, that the construction and capacity of the elements and particularly of the electric heater, are such that all of the water in the tank will be heated to a relatively high temperature and the electric heater will be deenergized before the expiration of the oil-peak period. It is evident that the adjustments of the various cooperating elements in my system may be made such that the period of energization of the heater I! may be made to coincide substantially with the mid-portion of the oil-peak period. It is, of course, also evident that the service man having charge of a number of such systems can so ar range them that the sum total of the current loads provided by such systems will be distributed as noted above, that is, substantially at the midportion of the oiT-peak period whereby no additional overload at the beginning of the off-peak period or at the end of the off-peak period will be caused on the circuits of the central station.

Various modifications may be made within the scope of my invention and it is desired that all modifications clearly coming within the scope of the appended claims shall be considered to be covered thereby.

I claim as my invention:

1. In an ofl-peak water heating system adapted for a heater and an electric circuit including said heater, a continuously operative timing means, a first switch for said heater actuable by said timing means and closable thereby for apredetermined length of off-peak time, an electromagnetic switch for said heater in series circuit with said first switch, a contact arm continuously movable by said timing means in accordance with time, a fixed contact on said timing means positioned to be engaged by said contact arm at the beginning or said oil-peak period, a thermostatic switch on the tank subject to the temperature of the water in the upper portion only of the tank and electric connections between said thermostatic switch, said electromagnetic switch, said contact, said contact arm and said electric circuit whereby said thermostatic switch is effective to cause energization of said electric heater when said contact arm engages said fixed contact and the temperature of the water operatively engaging said thermostatic switch is below a predetermined value.

2. In an oil-peak water heating system adapted for a water-containing tank having an electric heater and an electric circuit including said heater, a continuously operative timing means, a first switch for said heater actuable by said timing means and closable thereby for a predetermined length of off-peak time, an electromagnetic switch for said heater in series circuit with said first switch, a contact arm continuously movable by said timing means in accordance with time, a

fixed contact on said timing means positioned to be engaged by said contact arm at the beginning of said off-peak period, a thermostatic switch on the tank subject to the temperature of the water in the upper portion of the tank and electric connections between said thermostatic switch, said electromagnetic switch, said contact, said contact arm and said electric circuit whereby said thermostatic switch is eflective to cause energization of said electromagnetic switch and closure thereof when said contact arm engages said fixed contact and the temperature of the water operatlvely engaging said thermostatic switch is below a predetermined value and a second thermostatic switch efiective to cause deenergization of said electromagnetic switch and opening thereof in case substantially all of the water in the tank is l-lot before the end of an oil-peak period.

3. In an ofi-peak water heating system adapted for a water-containing tank having an electric heater, an electric circuit including said heater, a continuously operative timing means, a first switch in said circuit for controlling said heater and closable by said timing means for a predetermined length of off-peak time, an electromagnetic switch in said circuit and in series circuit with said first named switch for controlling said cheater, a contact arm continuously movable by said timing means in accordance with time, a first fixed contact on said timing means adapted to be engaged by said contact arm at substantially the beginning of the ofi-peak period, a thermallyactuable switch having a thermostat subject to thetemperature of the water in only the upper part or the tank, electrical connections between the switch and said first contact, said thermallylactuable switch being eflective to prevent energization of the electromagnetic switch and of the water-containing tank having an electric,

electric heater when the contact arm of said timing means engages said fixed contact and the temperature of the water in the upper part of the tank is above a certain value and a second fixed contact so positioned relatively to said first fixed contact as to be engaged by said contact arm a fixed length of time after it engaged said first fixed contact to thereby cause energization of said electromagnetic switch and of said electric heater.

4. In an oil-peak water heating system adapted for a water-containing tank havingan electric heater, an electric circuit including said heater, a continuously operative timing means, a first switch in said circuit for controlling said heater and closable by said timing means for a predetermined length of off-peak time, an electromagnetic switch in said circuit and in series circuit with said first named switch for controlling said heater, a contact arm continuously movable by said timing means in accordance with time, a first contact on said timing means adapted to be engaged by said contact arm at substantially the beginning of the old-peak period, a thermally-actuable switch having a thermostat subject to the temperature of the water in only the upper part of the tank and electrically connected to said first contact, said thermally-actuable switch being effective to prevent energization of the electromagnetic switch and of the electric heater when the contact arm engages said fixed contact and the temperature 0! the water in the upper part of the tank is above a certain value and a second fixed contact so positioned relatively to said first fixed contact as to be engaged by said contact arm a fixed length of time after it engaged said first fixed contact to thereby cause energization of said electromagnetic switch and of said electric heater and a second thermally-actuable switch effective to cause deenergization of said electromagnetic switch and of the electric heater in case substantially all of the water in the tank has been heated to a certain temperature before the end of an oil-peak period.

5. In an oil-peak water heating system adapted for a water-containing tank having an electric heater, an electric circuit including said heater, acontinuously operative timing means, a first switch in said circuit for controlling said heater and closable by said timing means for a predetermined length of oil-peak time, an electromagnetic switch in said circuit and in series circuit with said first named switch for controlling said heater, a contact arm continuously movable by said timing means in accordance with time, a plurality of peripherally spaced contact members on said timing means adapted to be engaged in sequence by said moving contact arm, a plurality of thermally-actuabl'e switches on said tank at longitudinally different points thereon, electric connections between the thermally-actuable switches and the contact members such that the topmost thermally-actuable switch is connected with the contact member engaged first by the moving contact arm, energization of the electromagnetic switch and of the heater being eilected by engagement of the contactarm with that contact connected to that thermallyactuable switch subject to cold water, whereby energization of the heater is delayed for lengths of time increasing with the amount of hot water in the tank.

6. In an off-peak water heating system. ada'pt-.

trio heater, an electric circuit including said heater, a continuously operative timing means, a first switch in said circuit for controlling said heater and closable by said timing means for a predetermined length of off-peak time, an electromagnetic switch in said circuit and in series circuit with said first named switch for controlling said heater, a contact arm continuously movable by said timing means in accordance with time, a plurality of peripherally spaced contact members on said timing means adapted to be engaged in sequence by said moving contact arm, a plurality of thermally-actuable switches on said tank at longitudinally different points thereon, electric connections between the thermally-actuable switches and the contact members such that the topmost thermally-actuable switch is connected with the contact member engaged first by the moving contact arm, energization of the electromagnetic switch and of the heater being effected by engagement of the contact arm with that contact connected to that thermally-actuable switch subject to cold water, whereby energization of the heater is delayed for a preselected fixed length of time increasing with the amount of hot water in the tank and an additional thermally-actuable switch positioned in the lowermost part of the tank eiIective to cause deenergization of said electromagnetic switch and of the electric heater in case the temperature of the water in the lowermost part of the tank has been raised to a certain value before the end of an oil-peak period.

7. In an oil-peak water heating system for a water containing tank having an electric heater, an electric circuit including said heater, 9. continuously operative timing means including a continuously movable contact arm indicating the time of day, a mechanically actuable switch in said moving contact arm at substantially the beginning of the off-peak period, a thermallythermally-actuable normally closed switch havperiod.

8. A device as set forth in claim 3 in which the peripheral extent of said first contact is appreciable to cause engagement theerof by the moving contact arm during a relatively long fixed time period and resultant energization of the tank heater at any time instant during such engagement between the contact arm and the first contact when withdrawal of hot water'from the tank causes said thermally-actuable switch to be operatively engaged by cold water in the tank.

9. A device as set forth in claim 6 in which the peripheral extent of each of said contacts is appreciable to cause engagement thereof by the moving contact arm during a relatively long fixed time period and resultant energization of the tank heater at any time instant during such engagement between the contact arm and the first contact when withdrawal of hot water from the tank causes said thermally-actuable switch to be operatively engaged by cold water in the tank.

CLARK M. OST'ERHELDl 

